There are conventional devices that carry out multi-step analytical procedures in an automated or semi-automated fashion. For example, microbiological analytical systems currently carry out automated antimicrobic susceptibility testing procedures using both photometric and fluorometric detection methods. The MicroScan Division of Baxter Healthcare Corporation sells a device of this type under the trade designation "Walk-Away." Armes et al. U.S. Pat. No. 4,676,951 and Hanaway U.S. Pat. Nos. 4,643,879 and 4,681,741 describe certain features the Walk-Away system.
Prior commercial embodiments of the Walk-Away system analyze trays carrying microbiologic specimens. The system includes an enclosed incubation chamber, where the trays are stored vertically stacked one above the other in compartments. When stored in the compartments, the trays are covered to prevent fluid loss by evaporation.
Prior commercial embodiments of the Walk-Away system periodically remove trays from the storage compartments to transport them to other work stations for the addition of reagents or for analysis by photometry or fluorometry. The trays are transported to these other work stations free of their covers, which remain behind in the storage compartments. The covers are placed back upon the trays when they are returned to the storage compartments.